Hey zurrain, first simple just start with one brush type and one color and start making marks.. seriously. Second look at tut from the desktop version website, this will give you an idea of the different tools. Third you'll find lots of video on youtube on mypaint, great place to see it in action. Lastly Tone has put together some great videos to see how to work on a small screen. Of course he's very talented so don't expect to be able reproduce what he does right away...

cheers

x